1. Field of the Invention
The present invention relates to an integrated circuit transformer, and in particular, to an integrated circuit transformer with a high coupling factor (k).
2. Description of the Related Art
Transformers are increasingly integrated on-chip for various analog and radio frequency (RF) circuit applications. One criterion of transformers is a high coupling factor (k). The coupling factor of a transformer is dependent on the portion of the total flux lines that cuts both primary and secondary windings of the transformer. A high coupling factor means high energy is transferred from the primary to the secondary windings, wherein there is low energy loss for the transformer during transference.
The amount of turn counts of the primary and secondary windings are normally increased for the conventional integrated circuit transformer to improve the coupling factor (k). However, more turn counts require larger layout areas, thereby increasing fabrication costs.
Thus, a novel transformer with a high coupling factor is desirable.